The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Does soy flour inhibit protease?

nicodvb's picture

Does soy flour inhibit protease?


I'm curious to know if soy flour can inhibit or slow down protease action in doughs. If so, what percentage is it safe to use with respect to flour? Does anyone have first hand experience with it?

I read some mention of it in baking applications, but nothing well explained.

If I werent sick at bed I would have tried it myself, but I have only whole (and very hard) soy beans  at home :-(




ananda's picture

 Hi Nico,

This is my understanding of why Soya flour is used:


Soya Flour

(no E number classification)

Not restricted used at up to 2% on flour weight

CARRIER or FILLER: to hold ingredients together and keep the mix flowing   Also a BLEACHING AGENT and a mild OXIDIZING AGENT, not easily demonstrated, but thought to act as an adjunct which will encourage the ascorbic acid to function

I've not come across any reference to its reducing capabilities, but I would refer you to Calvel, and his loathing of bean flour for further reference.   Main problem is dough oxidation, I believe, not protease.

Best wishes


nicodvb's picture

You are precious as always!

abdosoliman's picture

 Soy beans are exceptionally rich in proteins. Row soy bean contain a protease inhibitor Pi activity, it is heat sensitive. the role of the Pi is to prevent the  action of the seed protease during seed dormancy.

nicodvb's picture

Yes, soya flour and soy lecithin work equally well. I prepared  a biga with a touch of rye starter, some soya flour (around 8%, maybe I should have used less) and a weak flour. Next morning the biga had doubled and the consistence was still as stiff as the night before.

Same procedure for the lecithin, but I had to dissolve it in boilig water (2 gr in 100 gr of water).

The only annoyance was a touch of bad smell that I didn't like. Well, soya somewhat smells.